From The Editor
| January 11, 2018

Why Microplastics Are Still A Macro Problem For Wastewater Treatment Plants

The threat posed by microplastics, plastic beads smaller than 5 millimeters, has fallen on the nation’s wastewater treatment plants to address.

On the one hand, these substances do often originate at the home as a constituent of exfoliating and other household products, and cause damage to the environment only after they pass through wastewater treatment plants. On the other, these plants are rarely equipped with the tools necessary to eliminate such tiny contaminants. To help these burdened operations address the problem, a new effort between the University of Kansas (KU) and the National Science Foundation (NSF) looks to identify how microplastics are carried into waters, engage wastewater utilities through sampling, and create an online database of the results.

The study was inspired primarily because, while microplastics are clearly a pollutant in need of addressing, relatively little is known about their full impact or how best to reduce them.

“Microplastics have been and are an emerging issue in the realm of aquatic pollution for the past decade,” said Karl Rockne, NSF’s director for its Environmental Engineering Program. “We have comparatively few studies in the scholarly literature on their distribution and potential ecological effects in the environment, starting with international conferences about 10 years ago, and seminal papers on their prevalence in marine systems, and more recently, in freshwater ecosystems in the last few years.”

Revising Regulations

Accompanying this lack of insight has been some lackluster regulation. In 2015, following efforts in states like California and New York, Congress passed the “Microbead-Free Waters Act of 2015” to prohibit the manufacturing, packaging, and distribution of rinse-off cosmetics that contain plastic microbeads, over fears of how they were affecting source water. However, that action did nothing to address microplastics that could be entering waterways through cleaning products and clothing.

“Some regulatory agencies are considering how to handle this class of pollutants, but we are at the initial stages,” said Rockne. “We have seen some initiatives on some classes of microplastics, which are added to in consumer products, but these have not been done at a national scale.”

While the action two years ago indicated a federal commitment to getting microplastics out of the environment, at least under the Obama administration, it may be a lack of information regarding the complete microplastics picture that is holding back further regulation. But this additional rulemaking appears necessary, as the ban to cosmetics did not solve the problem.

“We know that microplastics are ubiquitous in the environment and are released to waterways from myriad sources,” Rockne said. “Much more needs to be studied to fully understand the loading to the environment, what happens to the particles once released, and what are their environmental impacts on human and ecological health.”

Efforts to combat microplastics have been targeted at the manufacturers of the products that contain them, but this may not always be the best way to address them. With the sources of contamination not fully understood and the environmental effects evident, it is certainly possible that wastewater treatment operations will be the ones tasked with eliminating them in the future.

“Wastewater treatment plants are the key interface between the urban water cycle … and the natural aquatic environment,’” said Rockne. “As such, wastewater treatment plants are a key location for control and prevention of releases.”

The Role Of Wastewater Treatment Plants

As KU and the NSF look for answers on microplastics, they will be teaming up with municipal wastewater treatment plants around the country during their three-year, $300,000 study.

“We’re going to be partnering with utilities across the country, and they’re going to sample their wastewater treatment plants, and we’ll quantify plastics release at wastewater treatment plants,” said Dr. Belinda Sturm, an associate professor of civil, environmental, and architectural engineering at KU and research lead of the study, per the university. “We’ll utilize [a U.S.] EPA database that shows how much flow is released by all plants in the country and we’ll use our measurements and this database of wastewater discharges to come up with a national release estimate.”

The researchers will also be looking at how microplastics might find their way into the biosolids that some wastewater operations sell or provide as fertilizer, introducing the contaminants to farmland and having them potentially enter water supplies as agricultural runoff.

With a better sense of just how many microplastics are escaping through wastewater treatment, a resulting database will help advocates and regulators understand the severity of the problem and may guide fundamental action. But in addition to this attempt to better understand the problem, the KU researchers hope to work toward a solution that can be directly applied by wastewater operations. They will be testing biofilms with extracellular polymeric substances (EPS) that may prove an effective barrier for microplastics.

“We think when there is more EPS in the system, we will get better removal,” Sturm said. “If I prove that to be true, then we can investigate how to get microorganisms to produce more EPS. If I can control that with engineering design and operation, I can improve removals.”

It will be some time before the project is able to quantity the problem with microplastics, and even more before regulators decide what to do with that information. Eventually, though, it’s an issue that will come back to the wastewater treatment plants that stand between contaminants and the environment.